1. Field of the Invention
The present invention relates to cleaning of interior surfaces which are difficult to access. In particular, the present invention relates to a method for cleaning the interior surfaces of a Bourdon Tubetype pressure gauge.
2. Description of the Prior Art
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure for the treatment of partial blockages in the coronary arteries. The most widely used form of percutanteous coronary angioplasty makes use of a dilation balloon catheter. The catheter is inserted into the patient's vascular system and guided, through the use of angiographic techniques, until the balloon at the distal end of the catheter is positioned within a stenosis. A radiographic contrast fluid is then fed under pressure through an inflation lumen of the catheter to the balloon, which causes the balloon to expand outward, thereby opening the stenosis.
During the expansion and contraction of the balloon, it is important for the operating physician to carefully control the pressure applied to the balloon through the radiographic contrast fluid. In a typical angioplasty apparatus, a pressure gauge, such as a Bourdon Tube-type pressure gauge, is attached to the radiographic contrast fluid pressure system. The pressure gauge is viewed by the operating physician and the pressure data thus obtained is used to adjust the radiographic contrast fluid pressure applied to the balloon.
Bourdon Tube-type pressure gauges are well known in this industry and provide adequate pressure information for a relatively low cost. Unfortunately, the interior of the Bourdon Tube of the gauge typically includes residues from manufacturing, particularly flux residues, which could contaminate the radiographic contrast fluid and thereby pose a danger to the patient.
In the past, the interior surface of the Bourdon Tube of a pressure gauge has typically been cleaned in the following manner. A small tube with a curved or angled orifice is inserted into the stem of the pressure gauge. The gauge and tube are then mounted in a rotable fixture and spun about the axis of the stem of the gauge at high angular velocities. This method relies upon centrifugal force to move wash fluid exiting the angled orifice into the Bourdon Tube of a gauge. Subsequently, the spinning is stopped, the gauge removed and a vacuum drawn to purge the wash fluid from the interior of the Bourdon Tube. An inert gas, such as nitrogen, is then used to fill the vacuum. The process is repeated three or four times.
The method of cleaning described above is expensive and time consuming, sometimes amounting to as much as four times the price of an uncleaned gauge. Further, the method is of doubtful effectiveness to actually clean the interior surfaces of the Bourdon Tube.